They're "mood buttons" but are part of whatever bulletin board programming (in our case here, PsychCentral's) and software, one can make one's own for one's own bulletin board or get from another bulletin board that has them but only use on one's own bulletin board/website, not someone else's.
Here's someone that made some for his own bulletin board:
http://help.forumotion.com/t31807-40-moods